An indication of extreme approval and admiration. May be used towards any entity or object one desires to express extreme approval and/or admiration for. however, usually not used to describe girls. Maybe used with the prefix "the essence of", or by itself.

ok:

-"How was the concert?"
-"Masterliness!!"

"Dark Side of the Moon by Pink Floyd is the essence of masterliness"

"The weather's masterliness"

Not ok:

"Damn, that girl's tits are the essence of masterliness!" <<this sounds corny